1. Field of the Invention
The present invention relates to a webbing retractor that takes-up and accommodates a webbing for restraining the body of a vehicle occupant seated in a seat.
2. Description of the Related Art
A locking mechanism, which restricts rotation of a reel shaft (a spool) in a pull-out direction at a time of rapid deceleration of a vehicle, is provided at a webbing retractor which structures a seat belt device of a vehicle, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 10-230817 for example. It is known that, in such a webbing retractor, when, from the state in which the webbing belt is pulled-out from the spool, the entire amount of the webbing belt is suddenly taken-up onto the spool due to the urging force of a take-up spring, a so-called end locking phenomenon may arise in which, due to the angular acceleration in the decelerating direction (negative angular acceleration) which arises immediately before completion of the taking-up and the shock applied to the spool at the time when the entire amount of the webbing belt is taken-up, the spool locking mechanism operates such that rotation of the spool in the pull-out direction is locked.
The webbing retractor of JP-A No. 10-230817 is equipped with a ratchet wheel which is supported so as to be able to rotate relative to the spool, and which operates the locking mechanism by causing a delay in rotation with respect to the spool; a lock arm which is pivotally-supported at the ratchet wheel so as to swing freely, and which meshes with internal teeth of a gear case so as to impede rotation of the ratchet wheel in the pull-out direction; and an inertial plate which is supported so as to be able to rotate relative to the spool, and which, when rotational speed in the webbing pull-out direction of a predetermined amount or more is applied, causes a delay in rotation with respect to the spool and swings the lock arm in the direction of the internal teeth of the gear case.
Further, in the above-described webbing retractor, due to rotation of the spool in the take-up direction after the spool is locked by the aforementioned locking mechanism, a cam portion, which is formed at the side end surface of one axial direction end side of the spool, pushes an arm portion formed integrally with the lock arm so as to swing the lock arm in a direction of canceling engagement with an engaged portion. In this way, if the spool is rotated slightly in the take-up direction, the locking of the spool by the locking mechanism can be released. Therefore, in a case in which end locking arises, if the webbing belt can be rewound slightly by forcibly pulling-out the belt and creating leeway in winding, the end locking can be cancelled.
However, the webbing retractor disclosed in JP-A No. 10-230817 does not prevent end locking in and of itself.